I 
HABITS OF A DIO DON 
13 
the limits of the tidal waves ; and as the rivulet slowly trickles 
down, the surf must supply the polishing power of the cataracts 
in the great rivers. In like manner, the rise and fall of the tide 
probably answer to the periodical inundations ; and thus the 
same effects are produced under apparently different but really 
similar circumstances. The origin, however, of these coatings 
of metallic oxides, which seem as if cemented to the rocks, is not 
understood ; and no reason, I believe, can be assigned for their 
thickness remaining the same. 
DIODON MACULATUS (DISTENDED AND CONTRACTED). 
One day I was amused by watching the habits of the Diodon 
antennatus, which was caught swimming near the shore. This 
fish, with its flabby skin, is well known to possess the singular 
power of distending itself into a nearly spherical form. After 
having been taken out of water for a short time, and then 
again immersed in it, a considerable quantity both of water and 
air is absorbed by the mouth, and perhaps likewise by the 
branchial orifices. This process is effected by two methods : the 
air is swallowed, and is then forced into the cavity of the body, its 
